Electrical and Optical Simulation of Organic Light-Emitting Devices: The Role of Emissive Layer Thickness

Optimizing the performance of organic light-emitting diodes (OLEDs) containing a dopant in the emissive layer (EML), requires the coupling of electrical and optical simulations to design device structures before proceeding to fabrication. Electrical or optical simulation alone, is not sufficient to properly optimize an OLED structure. By adjusting the conditions at the interlayer interfaces, taking into account defect states in the organic layers and controlling the thickness of the doped emissive layer in the ITO/NPB/Alq3(1%)/Alq3/LiF/Al structure, the performance of five different devices with different emissive layer thicknesses (15, 30, 45, 60, and 75 nm) has been studied. Structure characteristics analyzed included current density-voltage relationships, luminance-current density, position-recombination rate and electroluminescence spectrum. According to the results obtained, increasing the thickness of the emissive layer (EML) leads to a decrease in current density and turn-on voltage, affects the recombination rate and, consequently, the luminance and light spectrum, while the device with 30 nm thick EML has a clearer and higher maximum emission intensity than the other devices.